The invention relates to an armrest for a motor vehicle seat, which, with one end designed as a disk, is capable of being pivoted about a bearing journal, after the release of a locking device by raising its other end, with said end in the direction towards the seat surface, into a release position, and from there by again raising in the direction towards the seatback of the vehicle seat, about a specific pivot angle between two contact stop edges, into a locked position of use.
With an armrest of this kind, known from public use, the locking device consists of a pivotable engagement cam, which is arranged on the disk in a pivotable manner at a bearing pin, and in the position of use is supported by a projection at a first contact stop edge of the housing. When the other end of the armrest is raised, the engagement cam falls under its own weight against the second contact stop edge, which is formed from the free limb of a leaf spring mounted in a recess on the disk. The engagement cam is held in the release position, by this, and when the armrest is again pivoted upwards, it is pressed in front of the first contact edge of the housing into the position of use of the armrest. Because the engagement spring takes effect on the engagement cam only in the release position, protection against overload is not guaranteed. This leads to the situation in which, if the armrest is subjected to load by a person sifting on it, the engagement cam or the contact stop edge of the housing may break off, and the armrest rendered unusable. In addition to this, such a design requires an expensive aluminum decanting manufacture, of both the armrest and the housing. Finally, the engagement cam must also be manufactured from stamped steel, and the U-shaped leaf spring of spring steel.
With a second embodiment of the armrest, known from public use, of the type referred to in the preamble, the locking device consists of a sliding block capable of pivoting about a fixed-position pin in the housing, which is provided on its two narrow faces with V-shaped recesses, into which corresponding projecting contact edges of the disk of the armrest engage. In order to move the armrest from its position of use into its release position, the first contact edge of the disk, when raised, slides out of the V-shaped recess of the sliding block, in the direction of the seatback, the sliding block then being pivoted outwards as the second contact edge at the disk is raised further, out of the circular pivot path of the first contact edge of the disk, as a result of which the armrest can be pivoted downwards completely, in the direction of the seat surface, into its release position. When the armrest is raised again, the sliding block is pivoted around by the second contact edge into an engagement position with the first contact edge of the disk, so that with the subsequent repeated downwards pivoting of the armrest in the direction onto the seat, the first contact edge will engage in the other V-shaped recess, and a secure locking position, and therefore a position of use, of the armrest can again be guaranteed. This armrest likewise does not feature any overload protection, and requires, for the reinforcement of the middle section of the disk, which is made of plastic, appropriately stable and profiled insertion sheets made of steel.
Finally, an armrest of a different generic type is known from DE 39 40 895 A1, with which a locking pawl of fixed position, arranged so as to pivot about a bearing pin in the housing and under the effect of a bending spring engages in an outside tooth arrangement of the end of the armrest designed as a disk, in the position of use, and, when the armrest is raised, slides upwards against the force of a recovery spring over an oblique running surface at the disk, out of the teeth arrangement, onto a surface of the disk in the shape of a circle segment. This embodiment suffers from the disadvantage that on the one hand no overload protection is provided for the armrest, and, on the other, both the raising of the armrest into the release position as well as its pivoting downwards into its position of use is always effected against a pre-stressed recovery spring. This requires, at least at the raising of the armrest into the release position, additional force to be applied by the operating person, which under certain circumstances is not inconsiderable, which is ergonomically unfavorable. In the final analysis, this design presents an extremely complicated structure and is restricted to expensive metallic materials.
Taking this prior art as the basis, the objective on which the invention is based is of creating an armrest of the generic type referred to in the preamble, which with simple structural means will guarantee a reliable position of use, optionally with or without overload protection, ensures trouble-free and low-friction switching of the locking device for moving the armrest from its position of use into its release position and vice-versa, and can be made largely of plastic.
This objective is resolved, in conjunction with the generic concept according to the invention as described in the preamble, by the following features:
a) The locking device consists of a setting piston, capable of movement approximately radially to the bearing journal and under the effect of an engagement spring, with a transverse aperture and a locking slide capable of displacement therein,
b) The setting piston is provided at its end turned away from the engagement spring with an engagement projection, and engages with this, under the effect of the engagement spring, into an engagement recess,
c) The locking slide is capable of displacement in the transverse aperture of the setting piston between the two limbs of the pivot angle from a first contact edge into a locking fixed position, pushing the setting piston against the effect of the engagement spring, now still further prestressed, to the release position of the armrest, and
d) Is capable of displacement from a second contact edge into the position of use, leading to the locking of the armrest, releasing the setting piston to the effect of the engagement spring.
By means of these features an armrest is created with which, by means of the interaction of the end of the armrest, designed as a disk, in conjunction with the setting piston and the locking slide, a compact and highly efficient locking device is created, which, according to feature d), in the position of use, the engagement spring is released to take effect on the setting piston and therefore on its engagement projection. The features a), b) and c) guarantee an armrest which can be manufactured completely out of plastic, as far as the engagement spring and the bearing journal, in economical series manufacture. No maintenance is required, because the setting piston slides within its short displacement path on plastic surfaces, as the locking slide always does, which from the outset feature low friction coefficients. This also applies to the bearing journal made of metal, because this in turn is surrounded by an annular aperture of the disk of the armrest, said disk being made of plastic. The setting piston and the locking slide form a low-friction sliding switch with high strength, with the result that a low-friction and trouble-free switching of the armrest from its release position into its position of use and vice-versa can be effected at all times.
In an advantageous further embodiment of the invention, the setting piston features a square or rectangular external cross-section shape, and at its end turned towards the spring is provided with a recess to accommodate it, and, at its end turned away from the spring, is provided, either between two fork-shaped limbs, with a rotatable engagement roller, which engages in an engagement recess in the shape of a circle section, or with a rigid engagement projection engaging with positive fit into a corresponding positive-fit engagement recess. With the first alternative, overload protection is guaranteed, while with the second it is not.
In order for the engagement spring to be released or to be designed as weaker, it is to advantage for the axis of rotation of the engagement roller to be arranged with a smaller distance above or below the circular path in which the corresponding engagement recess is located. Due to the square or rectangular external cross-sectional shape of the setting piston, securing against rotation is provided.
The locking slide consists to advantage of a slide which is U-shaped in a front view, and otherwise cuboid in shape, of which the U-limbs feature differing widths. In conjunction with the setting piston described heretofore, the slide forms, with the disk, an extremely compact and flexurally-resistant locking device, which can extend almost across the entire width of the disk of the armrest. This locking slide is, in the release position of the setting piston, not subjected to any external forces worth mentioning, and in the locking position of the setting piston is subjected only to the force of the prestressed engagement spring. The locking slide does not take part in absorbing the forces conducted via the armrest, but is only displaced between the two end positions of the armrest, with low friction, by the two contact edges. It serves only to block or release the force of the engagement spring. The transfer of force is otherwise effected directly from the disk onto the setting piston and its engagement projection.
The faces of the two limbs of the locking slide form to advantage sliding surfaces, with which they can be pushed by the two contact edges on a counter-slide surface.
According to an advantageous further embodiment of the invention, the housing, which accommodates the end of the armrest designed as a disk and the bearing journal, features a fork-shaped housing body which encompasses the disk on both sides, and which is held at its closed web end by one of the frame bars of the seatback. As a result of this, all the parts of the locking device, namely the setting piston, the locking slide, and the spring are completely encapsulated in the housing and are therefore inaccessible to unauthorised access from the outside and therefore to incorrect operation. Reliable retention of the housing is guaranteed by the extremely compact and solidly-designed web end and by the stable frame bar of the seatback, as well as simple positioning.
According to a first advantageous embodiment of the invention, the engagement spring is supported with one of its ends in a recess of the end of the armrest which is designed as a disk, and with its other end in the recess of the setting piston, which is capable of displacement inside the same cut-out in the disk, and engages with its engagement projection in an engagement recess of the housing, whereby the first and second contact edges are arranged at the ends of a part circular path inside the housing and the slide surfaces for the locking slide are arranged in a flat cut-out on the disk of the armrest.
This embodiment guarantees, from the point of view of injection moulding technology, a simple design for the housing, of the locking slide, and of the end of the armrest designed as a disk. In mechanical terms, this embodiment features the advantage of an engagement projection arranged at a large lever arm relative to the bearing journal, which engages into an engagement recess arranged in the housing.
According to a second advantageous embodiment, the engagement spring is supported, in a kinematic reversal of the first embodiment, with one of its ends in a recess in the housing and with its other end in the cut-out on the rear end of the setting piston, which engages inside this cut-out in the housing in a displaceable manner and engages with its engagement projection in an engagement recess of the disk, whereby the locking slide is capable of displacement with sliding surfaces in circle segment shape on a circular path of the housing, and the first and second contact edge are arranged as projections at the disk of the armrest.
This embodiment does indeed feature a simple design, from the injection moulding point of view, of the end of the armrest designed as a disk, as well as of the housing, but the locking slide is of a complicated shape. In mechanical terms, this embodiment suffers in comparison with the first from the disadvantage of a shorter radial lever of the engagement projection in conjunction with the engagement recess in relation to the bearing journal.
Which of these two alternative designs is to be given preference depends both on the structural circumstances as well as on the purpose of use; in other words, for example, whether this armrest is to be used in a bus, a car, an aircraft, a train or tram, or on a chair or armchair in the domestic setting.
The effect of the engagement spring can be further increased by the engagement projection, consisting of a roller, being formed either from an entropy-elastic roller body or being provided with an entropy-elastic cylindrical casing, or being made of steel. With the first two options, two engagement springs are derived, arranged one behind another, so that a total spring hardness can be created without additional spatial requirement, in a rich range of variants, because in this case the entropy-elastic spring hardness of the roller takes effect as an additional engagement spring.
To guarantee overload protection for the armrest, for example if it is used as a seat, contrary to its intended purpose, the engagement spring or springs are pre-tensioned with the engagement projection in the engaged position, with such a spring force as will retain the armrest in its engagement position under a pressure force exerted on its free end of, for example, 5 kg, and only when this pressure force is exceeded will the engagement spring be compressed further under the effect of the returning setting piston, the engagement projection will be disengaged from the engagement recess into the release position of the armrest, and the latter will pivot downwards in the direction of the seat. As a result of this, the risk of breakage of the armrest and of the locking device in the event of improper use will be avoided.
The pressure force indicated of, for example, 5 kg, is therefore to be understood as indicative, since the person skilled in the art is at liberty to increase or reduce this pressure force by a corresponding spring pre-tension. The decisive factor is that the pressure force is to be dimensioned on the one hand in such a way that the support for the arm of a person will always be guaranteed, without the armrest disengaging from its locking position. On the other hand, account must also be taken of whether a child or an adult might make improper use of the armrest as a seat. If, for example, the pressure force on the armrest is increased to 30 kg, it would be possible for a child to sit on it, and, in the event of the armrest suddenly disengaging, the child would fall and might be involved in an accident. In order to exclude the risk of such accidents, the pressure force should always be set such that the locking device already disengages from the locking position under the weight of a child, without it suddenly falling down without warning, and, on the other hand, is still set sufficiently high for reliable support for the arm of an adult to be guaranteed. Such a pressure force is between about 3 kg and 5 kg.
The engagement spring and the bearing journal are made to advantage of steel, while by contrast all other parts are made of impact-resistant and form-stable plastic.
According to a particularly advantageous embodiment of the invention, the housing, the armrest, and the setting piston are made of polyamide 6 (PA6) with fibreglass reinforcement, or of polybutylene terephthalate (PBTP) and the locking slide of polyoxymethylene (POM). The latter material for the locking slide has proved to be especially suitable for sliding on PA6 or PBTP.